![]() ![]() Trying to sail through the narrow Jack Sound on the west coast of Wales can shorten the distance when heading north or south but the deep water channel between the rocks is just 200m wide and the rocks are mainly underwater. You can use the same technique in narrow channels where there are shoal patches or rocks that can be a danger. Patches of broken water, however, may confirm where the shallows are and reveal where the channel has shifted to. The charts and buoys may tell you one thing, but if there is breaking water across the entrance ahead, it would be foolish to plough on regardless, and better to stand off. Think about making an approach to a shallow entrance with a shifting seabed in an onshore wind, such as the Deben on the East Coast, Chichester Harbour bar, or Caernarfon Bar in North Wales. Much will depend on the size of the waves but you can be fairly sure that there will be breaking waves in any depth of less than 2.5m (8ft) when there are ocean waves rolling into the shore and these will allow you to identify the shallows. When you navigate using winds, remember sandbanks and shoals move frequently, so charts are rarely correct. The entrance to the River Deben is notorious for its dangerous bar. The problem of course is, what comprises a shallow patch? ![]() If there is shallow water and there is a swell running then you will almost certainly see the waves breaking on the shallow patches. ![]() This is why learning to navigate using waves is such a vital skill to have in your armoury. Satellite navigation is more accurate than ever, and with the advent of satellite receivers that can derive a position from several separate satellite constellations, they also have redundancy built in.Ī chartplotter screen gives the impression of indubitable accuracy, but datum shifts or, more likely, inaccurate or out-of-date chart data can throw a spanner in the works.Īdd in shifting coastlines, river mouths and sandbanks, and it would be foolish to rely solely on what the little glowing screen tells you about your location. Learning to interpret them is an art rather than a science, but is one that will give you an invaluable sense of your surroundings, and will alert you to danger when something doesn’t feel right.Įlectronic navigation has taken over our lives as navigators, even before GPS in the days of Loran C and Decca. The waves breaking on the rocks or reefs of an island would often be the first sign of land, but there are also more subtle and varied ways of reading the waves too. Indeed many of the ancient sea-going cultures also relied on waves for navigation. When voyages of discovery were being made 500 years ago and navigators had to make landfalls without any charts, being able to navigate using waves was a valuable technique, writes Dag Pike. ![]()
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